PERMO-CARBONIFEROUS BEDS IN THE STOCKHEIM BASIN/NE-BAVARIA - COALIFICATION AND ORGANIC GEOCHEMISTRY

Along the SW margin of the NE Bavarian Basement several Permo-Carboniferous basins are lined up, of which the northernmost Stockheim Basin is investigated best because of binuminous coal mining lasting until 1968 and succeeding uranium exploration. The sediments consist of greygreen, red and brown clastic and volcaniclastic rocks which accumulated in an alluvial fan. Coal formation took place at its distal parts. In places, weathering solutions led to syndiagenetic silicification of the coal. Uranium from these solutions was bound to organic matter and caused radioactive coalification in microscopical dimensions. In parts of the coal seam brecciated by post Permian fault tectonics base metal sulfides, pyrite and uranium black ores are enriched and in very restricted places coal is hydrothermally altered to char-like products. Vitrinite reflectance of the unaltered coal and of coaly substance from seven drillholes ranges between 0.89 and 1.74 % R(r). The coalification is attributed to very high temperatures caused by the igneous activity during the deposition of the Permo-Carboniferous series which is only 800 m thick. The organic-geochemical data support the microscopical findings and reveal a higher maturity of the organic matter compared to that of the Permo-Carboniferous Schmidgaden Basin situated further south. The sediments are characterised as gas source rocks by their extract yield.